Below guidelines for layout design can help to get
a better on-board performance.
- The decoupling capacitors
CVCC and CVLED for power supply must be close to the
chip to have minimized the impact of high-frequency noise and ripple from power.
CVCAP for internal LDO must be put as close to chip as possible.
GND plane connections to CVLED and GND pins must be on TOP layer
copper with multiple vias connecting to system ground plane. CVIO for
internal enable block also must be put as close to chip as possible.
- The exposed thermal pad must be
well soldered to the board, which can have better mechanical reliability. This
action can optimize heat transfer so that increasing thermal performance. The
AGND pin must be connected to thermal pad and system ground.
- The major heat flow path from the
package to the ambient is through copper on the PCB. Several methods can help
thermal performance. Below exposed thermal pad of IC, putting much vias through
the PCB to other ground layer can dissipate more heat. Maximizing the copper
coverage on the PCB can increase the thermal conductivity of the board.
- Low inductive and resistive path
of switch load loop can help to provide a high slew rate. Therefore, path of
VLED – SWx must be short and wide and avoid parallel wiring and narrow trace.
Transient current in SWx pins is much larger than CSy pins, so that trace for
SWx must be wider than CSy.